Lovastatin inhibits TGF-β-induced myofibroblast transdifferentiation in human tenon fibroblasts

PURPOSE. The transdifferentiation of Tenon fibroblasts to myofibroblasts is a pivotal step in filtering bleb scarring. It is mediated by the cytokine TGF-beta, Rho-dependent contractility, and cell-matrix interactions in an interdependent fashion. HMG-CoA-reductase inhibitors (statins) have been shown to inhibit Rho-GTPase signaling; therefore, the authors studied the influence of lovastatin on TGF-beta- mediated myofibroblast transdifferentiation to assess the potential use of statins in wound healing modulation. METHODS. Human Tenon fibroblasts were grown in culture, pretreated with lovastatin, lovastatin and mevalonate, or specific inhibitors of farnesyl transferase or geranylgeranyl transferase and were stimulated with TGF-beta 1. alpha-Smooth muscle actin (alpha-SMA) and connective tissue growth factor ( CTGF) transcription were assessed by real-time PCR. alpha-SMA protein expression and localization were studied by Western blot and confocal immunofluorescence microscopy. Cell contractility was determined in collagen gel contraction assays. Phosphorylation of the signaling proteins Smad-2/3 and p38 were detected by Western blot, and Smad-2/3 localization was determined by confocal immunofluorescence microscopy. RESULTS. Lovastatin inhibited TGF-beta-induced CTGF transcription, alpha-SMA expression and incorporation into actin stress fibers, and subsequent collagen gel contraction. These effects were reversed by mevalonate. The inhibition of geranylgeranyl transferase but not farnesyl transferase blocked TGF-beta-induced alpha-SMA expression. Lovastatin decreased TGF-beta-induced p38 activation, whereas Smad-2/3 phosphorylation and nuclear translocation were preserved. CONCLUSIONS. Lovastatin inhibits TGF-beta-induced myofibroblast transdifferentiation in human Tenon fibroblasts, most likely by interfering with Rho-signaling. Statins may, therefore, serve to inhibit scarring after filtering glaucoma surgery.